Effect of Nanoparticles on Cavitation in a Round Liquid Jet

Abstract

Nanofluid has drawngreatattentionas a new efficientenergy carrier for improving heat-transfer and combustionperformance. However, universalconsensus has not been reached on the mechanism of nanoparticlesinfluencing atomization and combustion. In this paper, the focus was thecavitation of Al2O3-H2O nanofluids inside and outside a nozzle with circular cross section. Comprehensive analyses of flow morphology were carried out based on a highspeed-macro shadow imaging system. The effects of nanoparticles on the initial development of round jet, incipient cavitation and supercavitation inside sharp-edge nozzle, and jet cavitationoutside round-edge nozzle were discussed. Results showed that: nanoparticles accelerated the formation of cavitation inside the nozzle, and reduced the critical supercavitation pressure. Meanwhile, they promoted the formation and persistence of bubbles in liquid jet. These bubbles generated near the KH-instability wave peaks below the nozzle. Compared with that of basic fluid, the wavelocationof nanofluid jet was closer to the nozzle exit. In conclusion, the addition of nanoparticlespromoted the cavitation inside and outside the nozzle.Itcan be attributed tothe following changes: nanoparticles increased the original adsorption of air, reduced the tensile strength of liquid, speeded up the disturbances of jet, and played the role of heterogeneous nucleation points.